I hear you. I love to figure out how these systems work and really need to know why something doesn’t work. I’m just often disappointed. 
Yes, there is a firmware update for the Marvels. It affects BT, but hard to say if it would affect your situation, but it might. It also lets you use the new MyPhonak app with more features and self-defined programs with limited program modifications.
Re: self update: do you do any HA programming currently? What I gather is you need a “Noahlink” wireless interface unit (available here), and “Target” software for the PC (not sure where you get it). Then you’d need to get the firmware file itself, though I think I saw it floating around somewhere on this forum.
I wouldn’t try it if you haven’t done any HA programming before and if you just want the update. But if you wanted to get into HA programming, go for it. There was a “DIY” thread I keep hearing about but I haven’t looked for/at it. It should help you get started.